Hepatitis B is usually induced by a hepatitis B virus (hereinafter, referred to as "HBV") and involves a major problem from immunological and clinical view points, but a sufficiently effective therapy has not yet been found. This disease is spread worldwidely and occurs particularly in Asia and Africa regions.
Effective prophylaxis of the disease is to administer an HBV vaccine and such a vaccine is practically used. The known HBV vaccine is usually prepared by highly purifying an HBs antigen obtained from blood plasma of a person infected inherently with HBV, so-called carrier, and inactivating the purified HBs antigen.
However, such a conventional vaccine must be subjected to safety tests in a chimpanzee in order to confirm that any infectious factors such as HBV or any other blood-origin viruses are not remaining in the vaccine, because it is obtained from blood. Besides, it is very difficult to get the chimpanzee for experiment. Thus, the conventional vaccine has some problems for industrial production thereof.
In order to eliminate such problems, many investigators have studied to obtain only HBs antigen on a large scale as the vaccine stock by utilizing DNA recombination technique, i.e. by introducing a DNA of HBV encoding HBs antigen protein into Escherichia coli or yeasts. Recently, it has been reported that the expression of HBs antigen by a recombinant was successful and the method could be used for the production of the antigen for practical use. Now, the last problem is how to purify the HBs antigen obtained by a recombinant in so high degree suitable for the desired vaccine stock or for diagnosis.